Delux

Adjusts the backlight intensity on laptops equipped with an ambient light sensor. Developed originally for the Acer C720, which has a software-enabled brightness sensor, but no userland tools which make use of it.

Delux should work on any Linux system, as long as the hardware has a light sensor and the kernel has the proper module loaded.

Delux is written in C and is lightweight on CPU. It uses a configurable table of values to precisely map ambient light sensor readings to appropriate screen brightness.

Installation

The latest source code can be found here.

To build and install delux, run :

./configure
make 
sudo make install

...and you're done!

To enable delux to start at boot, you can run :

sudo make enable

...which enables the init script at the end of boot, running from rc.local. For a more complete install, operating systems using upstart/sysvinit/bsdinit can update their init configurations to run the /etc/init.d/deluxd at boot time. Systems running systemd must use the rc.local method.

By default, the daemon runs as the root user, for hardware permision reasons. Future releases may use D-Bus / HAL to overcome this restriction.

Use

Delux is a freestanding binary, but is typically run as a daemon (deluxd). Root access is required to set the brightness level of the backlight, so both the binary and start script require root access to run.

To run the freestanding binary:

sudo /usr/local/sbin/delux

To run as a daemon:

sudo /etc/init.d/deluxd start

Brightness too high/low? Hitting your brightness +/- buttons recentres the daemon's reference brightness to the new level, and adapts to the user's setting on-the-fly.

If the laptop does not have a real sensor device, writing to the pseudo-device /dev/pals will set the apparent sensor value for the daemon. This is mostly only useful for testing purposes.

Configuration

Delux reads its configuration from /usr/local/etc/delux/luxtab.csv, which is a comma-separated value table. Each line represents one tuple of {sensorReading,brightnessSetting}. The default included luxtab is optimized for the Acer C720 -- each laptop manufacturer may have different sensor and brightness values. You may want to spend some time experimenting!

The build script does a good job at autoconfiguring the sensors and screen paths. However, if the udev package is not installed or the sensors are not properly detected, one may have to edit the paths.h file:

• sensorpath: The path to your light sensor. Usually found in /sys/bus/iio/devices/iio if the default does not already work. If no devices are found, or none are available on the system, it defaults to the fake-device /dev/pals.
• screenpath: The path to the backlight device for your screen. Usually this is found as /sys/class/backlight/$SCREEN/brightness -- $SCREEN will change based on manufacturer. The default $SCREEN is intel_backlight, which should work for most recent Intel integrated GPUs.
• luxtabpath: Path to the configuration CSV for delux. By default, this is /usr/local/etc/delux/luxtab.csv

ToDo

This program is by no means perfect. If you see where it can be improved, please suggest an improvement. Known ToDo's include:

• Hardware abstraction: D-Bus / HAL support and iio-sensor-proxy
• Full-feature init script (rc.subr, sysv, systemd?)
• Package for RPM / DPKG